The braod objective of the proposed research is to provide an integrated account of the cognition of autism that applies to both the cognitive and neural levels. The general approach is to determine how the cognitive system and the underlying neural systems are modulated by variations in the size and type of the processing demand that a task imposes. The brain imaging studies will use fMRI (functional Magnetic Resonance Imaging) in conjunction with previously tested functional neuroimaging paradigms for studing cognitive processes. The studies test the theory that the cognitive deficits that autistic individuals exhibit in higher level abstraction are due in considerable part to difficulties with executive processes that require extensive involvement of the prefrontal cortex. The studies will compare the cognitive performance and brain activity of individuals with autism to corresponding measures in age and IQ matched control subjects. In addition, key facets of language development and executive processing will be examined longitudinally (over a 3 to 5 year interval) in autistic children and adolescents and in control subjects, in both behavioral and brain imaging studies. The research will focus on three cognitive systems: the language comprehension system, the visuo-spatial processing system, and the executive processing system. Language comprehension will be examined with sentence comprehension and working-memory span tasks; visuo-spatial reasoning will be examined in the block design task and the mental rotation tasks; executive processes will be examined with the Tower of London task and a Piagetian reasoning task. The studies are expected to show that the visuo-spatial system is relatively spared in autism, although performance in visuo-spatial tasks can be impaired if the task places a large demand on executive processes. However, it is uncertain whether the language comprehension system is inherently impaired in autism, or alternatively, whether it produces impaired performance only in conjunction with an impaired executive system when executive processing demands are high. The converging multi-level approaches are expected to produce a characterization of autism that will provide new insights for therapy and and for facilitating daily functioning.